Wheelchair suspension

ABSTRACT

A wheelchair suspension includes a frame, a pivoting assembly, at least one front caster, and at least one rear caster. The pivoting assembly has a first link pivotally coupled to the frame member, a second link pivotally coupled to the frame member, a drive assembly fixedly connected to a first end of the first link, and a third link pivotally connected to the first link and pivotally connected to the second link. The drive assembly causes downward pivotal movement of the first end of the first link and upward pivotal movement of a second end of the first link. The upward pivotal movement of the second end of the first link causes the second link and the caster assembly to undergo upward movement.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a divisional of U.S. application Ser. No.14/585,393, filed Dec. 30, 2014, titled “Wheelchair Suspension,” whichis a continuation of U.S. application Ser. No. 13/465,268, filed May 7,2012, now U.S. Pat. No. 8,925,943, issued Jan. 6, 2015, titled,“Wheelchair Suspension,” which is a continuation of U.S. patentapplication Ser. No. 12/330,554, filed Dec. 9, 2008, now U.S. Pat. No.8,172,015, issued May 8, 2012, titled “Wheelchair Suspension,” which isa continuation of U.S. patent application Ser. No. 11/429,687, filed May8, 2006, now U.S. Pat. No. 7,472,767, issued Jan. 6, 2009, which is acontinuation of U.S. patent application Ser. No. 10/762,977, filed Jan.22, 2004, now U.S. Pat. No. 7,055,634, issued Jun. 6, 2006, which is acontinuation of U.S. patent application Ser. No. 09/974,348, filed Oct.10, 2001, now U.S. Pat. No. 7,040,429, issued May 9, 2006, thedisclosures of which are fully incorporated by reference herein in theirentirety.

FIELD OF THE INVENTION

The invention relates generally to conveyances and, more particularly,to wheelchair suspensions.

BACKGROUND OF THE INVENTION

Wheelchairs are an important means of transportation for a significantportion of society. Whether manual or powered, wheelchairs provide animportant degree of independence for those they assist. However, thisdegree of independence can be limited if the wheelchair is required totraverse obstacles such as, for example, curbs that are commonly presentat sidewalks, driveways, and other paved surface interfaces.

In this regard, most wheelchairs have front and rear casters tostabilize the chair from tipping forward or backward and to ensure thatthe drive wheels are always in contact with the ground. One suchwheelchair is disclosed in U.S. Pat. No. 5,435,404 to Garin. On suchwheelchairs, the caster wheels are typically much smaller than thedriving wheels and located both forward and rear of the drive wheels.Though this configuration provided the wheelchair with greaterstability, it made it difficult for such wheelchairs to climb overobstacles such as, for example, curbs or the like, because the frontcasters could not be driven over the obstacle due to their small sizeand constant contact with the ground.

U.S. Pat. No. 5,964,473 to Degonda et al. describes a wheelchair havingfront and rear casters similar to Garin and a pair of additional forwardlift wheels. The lift wheels are positioned off the ground and slightlyforward of the front caster. Configured as such, the lift wheels firstengage a curb and cause the wheelchair to tip backwards. As thewheelchair tips backwards, the front caster raises off the ground to aheight so that it either clears the curb or can be driven over the curb.

U.S. Pat. No. 6,196,343 to Strautnieks also describes a wheelchairhaving front and rear casters. The front casters are each connected to apivot arm that is pivotally attached to the sides of the wheelchairframe. Springs bias each pivot arm to limit the vertical movementthereof. So constructed, each front caster can undergo vertical movementwhen running over an obstacle.

SUMMARY OF THE INVENTION

The present invention relates to a wheelchair suspension that includes aframe, a pivoting assembly, at least one front caster, and at least onerear caster. The pivoting assembly has a first link pivotally coupled tothe frame member, a second link pivotally coupled to the frame member, adrive assembly fixedly connected to a first end of the first link, and athird link pivotally connected to the first link and pivotally connectedto the second link. The drive assembly causes downward pivotal movementof the first end of the first link and upward pivotal movement of asecond end of the first link. The upward pivotal movement of the secondend of the first link causes the second link and the caster assembly toundergo upward movement.

BRIEF DESCRIPTION OF THE DRAWINGS

In the accompanying drawings which are incorporated in and constitute apart of the specification, embodiments of the invention are illustrated,which, together with a general description of the invention given above,and the detailed description given below, serve to example theprinciples of this invention.

FIG. 1 is a perspective view of a wheelchair incorporating thesuspension of the present invention.

FIG. 2 is an exploded perspective view of certain components of thewheelchair of FIG. 1.

FIG. 3 is an exploded detail view of certain components of a side frameassembly of the present invention.

FIG. 4 is a side elevational view of the side frame assembly understatic conditions.

FIG. 5 is a side elevational view of the side frame assembly traversingan obstacle by ascending an obstacle.

FIG. 6 is a side elevational view of the side frame assembly traversingan obstacle by descending the obstacle.

DETAILED DESCRIPTION OF ILLUSTRATED EMBODIMENT

The present invention provides a wheelchair and suspension fortraversing obstacles and rough terrain. The present inventionfacilitates the traversing of obstacles and rough terrain by allowingfor the vertical and lateral movement of one or more front casterassemblies coupled to the wheelchair.

Referring now to FIG. 1, a perspective view of a wheelchair 100 of thepresent invention is shown. Wheelchair 100 is preferably a mid-wheeldrive or rear-wheel drive wheelchair. As shown, wheelchair 100 has achair 102 having arm supports 104 and 106. A control device such as, forexample, a joystick controller 108 is attached to the chair 102 forcontrolling any power-related aspects of wheelchair 100. Wheelchair 100further has removable decorative shrouds 110 covering the wheelchair'ssuspension, drive, and control systems. Projecting forward from theshrouds 110 is footrest 112 for supporting the feet of the wheelchair'suser.

Illustrated in FIG. 2 is an exploded perspective view of certaincomponents of wheelchair 100. The suspension system has a sub-frame 200for accommodating, among other things, removable batteries 226 and 228.Removably attached to sub-frame 200 are first and second side frameassemblies 202 and 204. Side frame assemblies 202 and 204 are removablyattached to sub-frame 202 via interfaces preferably in the form ofspring loaded hooks and latches. The spring loaded hooks preferablyreside on sub-frame 200 with the corresponding latches residing onside-frame assemblies 202 and 204. In this manner, an individual canmanually without the use of tools take apart wheelchair 100 for easytransportation in, for example, the trunk of a car or other largevehicle.

Each side frame assembly has at least one drive assembly having a motordrive 210 and 212 and a drive wheel 206 and 208. Each motor drive 210and 212 preferably has either a motor/gear box combination or abrushless, gearless motor. Each side frame assembly further has at leastone front caster assembly 218 and 220 coupled thereto via pivotingassemblies 214 and 216. At least one rear caster assembly 222 and 224are also provided for each side frame assembly. Each of the side frameassemblies are identical in construction and, hence, the presentdiscussion will focus on describing side frame assembly 202 with theunderstanding that such discussion is equally applicable to side frameassembly 204.

Referring now to FIG. 3, an exploded detailed perspective of certaincomponents of side frame simply 202 is shown. In this regard, side frameassembly 202 has a side frame member 301 having sub-members 302, 304,306, and 318. These side frame sub-members are preferably tubular (i.e.,circular, oval, or rectangular in cross-section) and formed and weldedtogether has shown. Pivoting assembly 214 has a first pivoting linkage319 defined by sub-linkages 320, 322, 324, and 326. These sub-linkagesare also preferably tubular in configuration, as described above, andformed and welded together as shown. Sub-linkage 326 has a motor driveassembly mounting bracket 328 attached thereto. A second pivotinglinkage 334 is also provided. As shown in FIG. 3, the overall length ofthe first pivoting linkage 319 is greater than the overall length of thesecond pivoting linkage 334. As will be presently described, thisconfiguration facilitates, for example, the dual functions of liftingand retracting the front caster assembly 335 away from the obstacle tobe traversed and inward toward the wheelchair.

The first pivoting linkage 319 is pivotally coupled to side frame member301 via tubular stud or extension 308. The second pivoting linkage 334is pivotally coupled to side through member 301 via tubular stud orextension 312. A compression plate 332 is provided for additionalstability and is coupled to side frame member 301 via tubular studs orextensions 308 and 312 and pivot stop member 310.

Resilient extension springs 344 and 346 are provided between side framemember 301 and first pivoting linkage 319. In this regard, spring 344has a first connection to frame member 301 via bracket 314 and a secondconnection to first pivoting linkage 319 via bracket 330. Spring 346 hasa first connection to frame member 301 via bracket 316 and a secondconnection to first pivoting linkage 319 via bracket 348. As will bedescribed in more detail, extension springs 344 and 346 are connected tofirst pivoting linkage 319 on either side of the linkages pivotalconnection to side frame member 301 and provide a unidirectional biasforce around the first pivoting linkage 319 pivotal coupling to sideframe member 301. Alternatively, resilient elastomeric members can beintegrated into the pivotal coupling between first pivoting linkage 319and side frame member 301. Similarly, resilient elastomeric members canbe integrated into the pivotal coupling between second pivoting linkage334 and side frame member 301. Such resilient elastomeric members can be“Rosta”-type bearings or other similar structures.

A front caster assembly 335 is pivotally coupled to each of the firstand second pivoting linkages 319 and 334. In this regard, front casterassembly 335 has an integral head tube/bracket 336 for receiving acaster fork 337 and making the aforementioned pivotal couplings tolinkages 319 and 334. These pivotal couplings to linkages 319 and 334are facilitated by first and second holes 338 and 340 in headtube/bracket 336 and corresponding tubular formations in first andsecond pivoting linkages 319 and 334. A rear caster is attached to sideframe assembly 301 via rear caster fork 342, which is received insub-frame member 318.

Configured as such, first and second pivoting linkages 319 and 334 pivotwith respect to side frame member 301. Moreover, front caster assembly335 undergoes spatial displacement with the pivotal movement of firstand second pivoting linkages 319 and 334. The rear caster wheel and fork342 are generally not affected by the pivotal movement of first andsecond pivoting linkages 319 and 334.

Referring now to FIG. 4, an outer side elevational view of side frameassembly 202 is shown under static conditions (i.e., the wheelchair isstanding still or neither accelerating or decelerating). Drive wheel 206is only partially shown so to not obscure the relevant components ofside frame assembly 202. In this state, all wheels including the drivewheels and front and rear caster wheels are in contact and maintaincontact with the ground or other riding surface.

Referring now to FIG. 5, an inner side elevational view of side frameassembly 202 is shown as the wheelchair traverses an elevated obstacle.The component displacement shown in FIG. 5 normally occurs when thewheelchair is quickly accelerated forward to traverse an obstacle suchas curb 500. For purposes of the present discussion, the pivotalcoupling between first pivoting linkage 319 and side frame member 301 isdesignated by pivot P1. Similarly, the pivotal coupling between thesecond pivoting linkage 334 and side frame member 301 is designated bypivot P2. In relationship to each other, it can be seen that pivot P2 isbelow and laterally offset from pivot P1 in a direction toward the frontcaster. In other words, pivot P2 is laterally closer to front casterassembly 335 than is pivot P1. In combination with the respectiveoverall lengths of first and second pivoting linkages 319 and 334, thisconfiguration provides the dual functions of lifting and retracting thefront caster assembly 335 away from the obstacle to be traversed andinward toward the wheelchair.

In this regard, when the wheelchair is accelerated forward by a highrate, the resulting moment arm generated by the drive wheel 206 willexceed the resultant moment arm generated by springs 344 and 346. Thiscauses first pivoting linkage 319 to pivot or rotate in a clockwisedirection about pivot P1 thereby raising front caster assembly 335. Thismotion also causes second pivoting linkage 334 to undergo pivotalmotion. The resulting effect of second pivoting linkage 334 motion is tocause front caster assembly 335 to pivot about its pivotal coupling 338to first pivoting linkage 319. This pivotal movement causes front casterassembly 335 to be drawn inward toward the wheelchair itself and awayfrom the obstacle 500 being traversed. The maximum amount of pivotalmovement is limited by stop 310, which physically engages side framemember 301 sub-linkage 320. The same effect described above is achievedshould side frame assembly 202 be driven directly over obstacle 500.Once the resultant movement arm generated by drive wheel 206 is lessthan the resultant movement arm generated by springs 344 and 346 withrespect to pivot P1 front caster assembly 335 is lowered.

Referring now to FIG. 6, an inner side elevational view of side frameassembly 202 is shown as the wheelchair traverses descends an obstacle600. In this regard, the resultant moment arm generated by springs 344and 346 is greater than any other moment arm around pivot P1. Thiscauses first pivoting linkage 319 to rotate counter-clockwise and tolower the front caster assembly 335 on the lower supporting or ridingsurface. In this regard, the respective position of pivot P2 and theoverall length of second pivoting linkage 334 compared to the positionof pivot P1 and the overall length of first pivoting linkage 319 providefor front caster assembly 335 to descend to the lower supportingsurface. Concurrently therewith, the pivotal motion of second pivotinglinkage 334 causes front caster assembly 335 to pivot about its pivotalcoupling 338 to first pivoting linkage 319. This motion causes frontcaster assembly 335 to extend forward. The combined effect of loweringand extending front caster assembly 335 provide the wheelchair withgreater stability when descending a obstacle because the wheelchair issooner and longer in contact with the differing elevations thatrepresent the obstacle. The maximum pivotal movement is once againlimited by stop 310, which physically engages side frame member 301sub-linkage 322 in this scenario.

Hence, the present invention facilitates the traversing of obstacles andrough terrain by allowing for the vertical and lateral movement of oneor more front caster assemblies.

While the present invention has been illustrated by the description ofembodiments thereof, and while the embodiments have been described inconsiderable detail, it is not the intention of the applicant torestrict or in any way limit the scope of the appended claims to suchdetail. Additional advantages and modifications will readily appear tothose skilled in the art. For example, a plurality of casters can beused instead of one caster, the casters can be coupled to the pivot armsvia shock absorbing fork assemblies, and the specific locations of thepivotal couplings can be modified so long as the above-described overallrelationships are maintained. Therefore, the invention, in its broaderaspects, is not limited to the specific details, the representativeapparatus, and illustrative examples shown and described. Accordingly,departures can be made from such details without departing from thespirit or scope of the applicant's general inventive concept.

1. A wheelchair suspension defining a forward direction and a rearwarddirection of the wheelchair, the suspension comprising: a frame; atleast one main drive wheel for engaging the ground; at least one frontcaster for engaging the ground forward of the main drive wheel; and apivoting assembly mounting the front caster to the frame so that thefront caster can move upwardly and rearwardly when encountering anobject, the pivoting assembly comprising an upper link and a lower link,the upper link being pivotally mounted to the front caster and to theframe at respective upper pivot axes, the lower link being pivotallymounted to the front caster and to the frame at respective lower pivotaxes, the distance between the upper pivot axes being different than thedistance between the lower pivot axes.
 2. The wheelchair suspension ofclaim 1, further comprising at least one rear caster for engaging theground rearward of the main drive wheel, the front caster and rearcaster being mounted with respect to the frame so that the front caster,the main drive wheel and the rear caster can all engage level ground atthe same time, and further wherein the front caster is biased tonormally remain in contact with the ground.
 3. The wheelchair suspensionof claim 1, wherein the front caster is biased to remain in contact withthe ground.